Project Summary/Abstract It is increasingly evident that both soluble factor-mediated chemical signaling and physical force-mediated mechanotransduction play critical roles in living cells and tissues. Yet we know relatively little about how force regulates gene expression and vital biological functions. Mechanosensors at or near the cell surface such as integrin, talin, or vinculin have been reported, but whether the nucleus itself and its chromatin can act as a mechanosensor is an unanswered question in the field of mechanobiology. Yet regulation of gene expression in normal cells and cancer cells is one of the most critical processes that control cellular functions and behaviors. This research project aims to understand how forces and mechanical microenvironment directly influence gene expression and to identify intra-nuclear proteins that are responsible for mediating force transfer from nuclear lamina to lamina-associated domains of chromatin in living cells. Our preliminary results strongly suggest that a local physiologically-relevant force via integrins can directly upregulation transcription via stretching the chromatin in living cells. Built on these results, we propose 3 specific aims to elucidate mechanotransduction mechanisms in the living cells. Aim 1: to test the hypothesis that chromatin stretching is required for direct transcription upregulation by force via integrins; Aim 2: to test the hypothesis that force via integrins directly activates mechanosensitive genes more than housekeeping gene DHFR; Aim 3: to dissect out the mechanism of gene repression in response to high forces and on stiff matrices. Our experimental designs are rigorous and the likelihood of generating insightful discovery is very high. The long-term goal is to develop novel strategies to intervene the processes that regulate gene expression in living cells in animals and human subjects to treat and cure diseases like malignant tumors.